Flashcards in Chapter 14: Independent Group tTest Deck (23):
1
When do you go by correlated group design?
 Null hypothesis population u and o are unknown
 differences between PAIRED scores are analyzed.
2
Experiment with two conditions?
 random sampling of subjects from population.
3
What are the characteristics of Independent groups design?
 ____ of subjects from population
 _____ assignment to each condition
 Each subject is tested how many times?
 What are analyzed?
 ttest analyzes what?
 Random sampling of subjects from population
 Random assignment to each condition
 No basis for pairing of scores
 Each subject is tested ONLY once
 Raw scores are analyzed
 ttest analyzes difference between sample means.
4
What are the alternative hypotheses for Directional and Nondirectional?
 U1 > U2 or U1 U1 does not = U2 (nondirectional)
5
What are the null hypotheses for Directional and Nondirectional?
 U1 <= U2 ( directional )
 U1 = U2 (nondirectional)
6
Sample scores from condition 1 include:?
 U1= mean of pop that receives condition 1
 O1 = standard deviation of the pop that receives condition 1.
7
Sample scores from condition 2 include:?
 U2= mean of pop that receives condition 2
 O2= standard deviation of the pop that receives condition 2
8
What is the major assumption of independent groups design?(3)
 changing level of IV affects MEAN ONLY
 Does not affect standard deviation or variance
Therefore: O^2 1 = O^2 1
 If IV has a real effect the means will differ, not variance
L> IV assumed to equally affect each individual
9
Sampling distribution of the difference between sample means ( X1X2):
 Draw all possible samples of __ and ___, from a population of __ and __, and standard deviation of __ and __.
 Calculate __ and __ for each sample
 Calculate ____ for all possible pairings of samples of size __ and __.
 n1, n2, u1, u2, o1, o2
 Xbar 1, Xbar 2
 Xbar 1 Xbar 2
 n1 and n2
10
What is the formula for ttest of independent groups?
 Tobt = (X1X2)  uX1 uX2/ square root of: S^2w( 1/n1 + 1/n2)
 S^2w = weighted estimate of o^2 (variance)

11
What is the computational equation for tobt???
 tobt= (X1X2)/ square root: (SS1+SS2/n1+n22) times by (1/n1+1/n2)
12
What is the formula for df for independent groups?
 N2
13
Conclusion for independent groups? (t)
  tobt  >=  tcrit , reject Ho
14
What is the formula for Tobt when n1=n2 ?
degrees of freedom ?
 Tobt= (X1X2)/ square root of: SS1+SS2/ n(n1)
 Df= N2 (N= population NOT SAMPLE)
15
What is the assumption of independent group ttests?
 test is robust
16
The sampling distribution is ___ distributed. If __=__ and _>=_.
 normally
 n1=n2
 n>= 30
17
Homogeneity of variance? huh?
 O1^2 = O2^2
L> Mann Whitney U
18
What is the formula for effect size of independent groups?
 D=  X1 X2 / square root of: S2w
ala > S2w= SS1+ SS2/ n1+n22
19
What increases power??
 Great effect of IV
 Larger sample size
 Decreased variability
20
Correlated ttests is more powerful when correlation between paired scores is __.
 high
21
What is the equation for confidence intervals?
 95%
 99%
 u lower= (X1X2) Sx1x2 t0.025
 u upper= (X1X2) + Sx1  X2 t 0.025
 u lower= (X1X2) Sx1X2 t 0.005
 u upper= (X1X2) + SX1 X2 T 0.005
22
SX1X2=??
SQUARE ROOT OF: SS1+SS2/n1+n22)(1/n+1/n2)
23